Circulation control for boilers



March 15, 1949. RM. NALVEN y 2,464,750

l CIRCULATION CONTROL FOR BOILERS INVENTOR.

Filed March 1, i944 Zahvfi f4. )Va/ym BY Patented Mar. 15, 1949CIRCULATION CONTROL FOR BOILERS Robert M. Nalven, Kew Gardens, N. Y.,assignor,

by mesne assignments, to Combustion Engineering-Superheater, Inc., NewYork, N. Y., a

corporation of Delaware Application March 1, 1944, Serial No. 524,535

8 Claims. (Cl. 122-411) This invention relates to steam generators andparticularly to those having forced Water circulation.

In boilers where Water is circulated from a steam and Water separatingdrum through steam generating tubes and back to the drum by means Iof apump, there is a possibility of loss of service of the unit due tofailure of the pump and to meet this situation it has been customary toprovide duplicate pumps. Since the weight of water is about five or moretimes the Weight of steam generated by the boiler at full load thecirculation pumps are relatively large and each additional pumpincreases the space occupied by the boiler unit and also requiresadditional piping and valves. The necessity of utilizing space in thisway and the complication of pipe Work is particularly objectionable inmarine boiler installations where both weight and space are critical andsimplicity a consideration of design. Thus, it would be desirable toomit all but one of the circulation pumps were it not for the handicapof relying upon a single pump for circulation of the boiler water.

It is an object of this invention to overcome the above mentioneddisadvantages by providing a novel arrangement for insuring circulationof the boiler Water through the steam generation tubes if thecirculation pump fails.

In the drawings:

Figure 1 is a diagrammatic elevational view of a steam boiler embodyingthe invention.

Figures 2 and 3 are diagrammatic illustrations of diaphragm operatedvalves utilized in the water circulating system of Figure 1; and

Figure 4 is a fragmentary View showing an alternative arrangement.

The steam boiler comprises a steam and Water separating drum I connectedto the steam and water tubes and by means of downcomer pipe II to aWater circulating pump I2. Steam evaporation tubes I4, of which oneappears in Fig. 1, are connected at one end to a distribution header I5supplied by pump I2 and at their other ends discharge into the steam andwater drum IIJ. The pump I2 is connected to distribution header I5 bymeans of a pipe I6 having a check valve II interposed therein. BoilerWater is circulated by means of pump I2 through the steam evaporation Ytubes I4 at rates equal to several times the Weight `of motors 33 and3'Iv as desoribed'above.

in the furnace oitake 3 are located a superheater 2 and an economizercomprising a multiplicity of tubes 25 arranged in parallel alinement indirections perpendicular to the plane of the drawing and receiving Waterfrom a boiler feed pump 26. The Water from all economizer tubes passesinto a header 28 and via pipes 3b, 3l with interposed valve 32 to thesteam and Water drum Ill. From pipe 30 a branch connection 33 with valve34 leads to Water distribution header I5. Water from economizer header28 may thus be optionally directed via pipe 3D, valve 32 and pipe 3| tothe steam and'water drum I0 or via valve 34 and pipe 33 to distributionheader I5. `A check valve 35 may be mounted in pipe 33 as shown in Fig.4 and valve 34 omitted.

Valves 32 and 34 may be hand controlled but are preferably operatedautomatically by motors 36 and 31 responsive to the ow of Water in thecirculation pump discharge I6. Said flow of Water may be measured by thepressure developed by pump I2 or by the differential pressurebetween thepump discharge I6 and' pressure in the boiler drum. Motors 3S and 31 maythen .employ diaphragms which act upon the seats of valves 32 and 34 ina known manner as `shown in Figs; 2 and 3, to either close or open themagainst ,the resistance of springs.,r The diaphragms of motors 35, 31are subject to the pressure of the pump discharge on one side throughpipes 38 and 39 respectively, on the sides of the diaphragms farthestAfrom the valve discs and steam drum pressures may be transmitted fromthe `pipes ,38, 3| into the valve bodies and Vthrough the valve stemhousings to the side of the diaphragms nearest to the valve. l

In operation pump I2 delivers Water to header I5 at a' pressuresuiiiciently above boiler pressure to overcome the resistance of theevaporation tube circuits I4 when pumping the required Weight of watercorresponding to a certain steaming rateof the boiler.` The weight ofboiler water circulated through the evaporation tubes I4 may be ve timesor more that of the steam being evaporated in these tubes. When pump I2fails, valve 32, which is normally open, will be closed,andsimultaneously valve 34, which is normally closed, is opened, both ofwhich operations may be effected by hand or automatically because ofdecrease of pressure on the top of the diaphragms Check valve I1 alsocloses'due to loss of circulation pump pressure and feed Water from pipe3l] is then delivered through pipe 33 (through check valve 3 if present)to header I5.

If the check valve 35 is installed, valve 34 may be omitted. The pump l2delivery pressure is substantially above the pressure in the feed waterpipe 30 leading from the economizer header 28 to the drum lll and thecheck valve 35 (Fig. 4) is normally kept closed due to this pressuredifference and is opened by the feed Water in line 33.

The feed water supplied to header l5 is equal in weight to the steambeing evaporated and hence the pressure drop through the evaporationtube circuits i4 will be relatively small since the resistance throughthese circuits will vary approximately as the squares of the relativevelocities. The pressure required in the pipe 33 above that of theboiler pressure in the drum l0 need then be only suicient to overcomethe reduced pressure drop through the evaporator tube circuits I4, sothat this added pressure superimposed upon the boiler feed pump pressureis negligibly small and does notinvolve any increase in the size of feedpump Z6. For example, if the normal discharge pressure of pump l2 isthirty-five pounds above boiler pressure when delivering water at a ratefive times the weight of steam evaporated, then increase in dischargepressure for feed pump Z6 to deliver Water through header I5 into theevaporation tubes i4, at a rate equal to the weight of steam evaporated,will be but about two pounds.

Thus the invention renders it possible to employ a single circulationpump for a forced water V,circulation boiler in combination with aboiler feed pump of normal size and still maintain a forced circulationof water through the boiler evaporation tubes upon failure of thecirculation pump.

What I claim is:

1. In a steam boiler having steam generating tubes connected todischarge into a separating drum to which a circulation pump isconnected for supplying said tubes with water taken from said drum, anda Second pump connected by piping to supply `feed Water to said drum; aSelfclosing valve in said piping; a conduit connecting said piping at apoint ahead of the valve therein in the direction of water flow with theadmission ends of said tubes; a self-opening valve in said conduit; andmeans responsive to the normal delivery pressure of said circulationpump for maintaining said self-opening valve closed and saidself-closing valve open to prevent feed water -from entering said tubesduring the delivery of lnormal pressure by said circulation pump.

2. In a steam boiler having steam generating tubes connected todischarge into a separating drum to which a circulation pump isconnected for supplying said tubes with water taken from said drum, acheck valve located in the connec tion between said tubes and pump andarranged to be opened by normal delivery pressure of the latter; and asecond pump connected by piping to supply feed water to said drum; a4valve in said piping; means responsive to the normal delivery pressureof said circulation pump to maintain said valve open as long as thecirculation pump produces said normal pressure; a conduit connectingsaid piping at a point ahead of the valve therein in the direction ofwater iiow with the .admission ends Q f .Said tubes; :f1-valve in .Said60n- Lduit; means responsive to the normal delivery lpressure of saidcirculation pump to -maintain said `last named valve closed as long asthe circulation pump produces said -normal pressure; and meansresponsive to decrease of the circulation pump delivery pressure tobelow said normal value for I closing said first mentioned valve and foropening said second mentioned valve so that the feed pump may supplyWater to said tubes rather than said drum upon outage of saidcirculation pump.

3. In a steam boiler having steam generating tubes connected todischarge into a separating drum to which a circulation pump isconnected for supplying said tubes with Water taken from said drum, acheck valve in the connection between said tubes and pump arranged to beopened by the pumps normal discharge pressure, and a second pumpconnected by piping to supply feed water to said drum; a valve in saidpiping; means responsive to the normal discharge pressure of saidcirculation pump to maintain said valve open as long as the circulationpump produces said normal pressure and means to close the valve when thepump discharge pressure drops substantially below normal; a conduitconnecting said piping at a point ahead of the valve therein in thedirection of water flow with the admission ends of said tubes; and acheck valve in said conduit disposed to be closed by the said normaldischarge pressure of said circulation pump.

4. In a steam boiler having steam generating tubes connected todischarge into a separating drum to which a circulation pump isconnected for supplying said tubes with water taken from said drum, acheck valve in the connection between said tubes and pump arranged to beopened by normal delivery pressure of the latter, and a second pumpconnected by piping to supply feed water to said drum; a valve in saidpiping; means responsive to the normal delivery pressure of saidcirculation pump to maintain 'said valve open as long as the circulationpump produces said normal pressure; a conduit connecting said piping ata point ahead of the valve therein in the direction of water flow withthe admission ends of said tubes; a valve in said conduit disposed to benormally closed by the delivery pressure of said circulation pump; andmeans responsive to decrease of the circulation pump delivery pressureto below said normal value for closing said first mentioned valve sothat the feed pump may supply water to said tubes rather than said drumupon outage of said circulation pump.

5. In a steam boiler having steam generating tubes connectedizo-discharge into a Vseparating drum to which a circulation'pump isconnected for supplying said tubes through a pipe with water taken fromsaid drum, and a second pump connected by piping to supply feed water tosaid drum; a valve in said piping; means responsive to the normaldelivery pressure of said circulation pump to maintain said valve openas long as the circulation pump produces said normal pressure; a conduitconnecting said piping at a point ahead of the valve thereininthe'direction of Water new with the admission ends of said tubes; acheck valve in said conduit disposed to be closed by said normalcirculation pump `delivery pressure; a check valve in said pipe disposedto be opened by said normal circulation pump delivery pressure; andmeans responsive to 'decreaseA of the delivery pressure of saidcirculation pump to below said normal value for closing said vfirstmentioned valve so that the feed lwater pump may supply water t0 Saidtubes .rai-lier than saisi drum uP9n.

outage of said circulation pump.-

6. In a steam boiler having 'a water separator with steam generatingtubesJ connected thereto, a circulation' pump, apipe connecting the pumpinto the boiler circulation in series with the generating tubes, a checkvalve in said pipe arranged to be opened by the normal delivery pressureof said circulation pump, and a boiler feed pump; piping connecting saidfeed pump to the steam generating tubes beyond said check valve withrespect to the direction of circulation; a branch pipe connecting saidpiping with the separator; a self-closing valve in the branch pipe; acheck valve in the piping connecting the feed pump to the steamgenerator' tubes preventing flow from said circulation pump through saidpiping; and motor means responsive to the production of normal dischargepressure by the circulation pump for maintaining open the saidself-closing valve in the branch pipe whereby then to permit flow fromsaid feed pump into the separator.

7. In a steam boiler having a water separator with steam generatingtubes connected thereto, a circulation pump, a pipe connecting the pumpinto the boiler circulation in series with the generating tubes, a checkvalve in said pipe arranged to be opened by the normal delivery pressureof said circulation pump, and a boiler feed pump; piping connecting saidfeed pump to the steam generating tubes beyond said check valve withrespect to the direction of circulation; a branch pipe connecting saidpiping with the separator; a valve in the branch pipe connecting thefeed pump to the separator; means responsive to the normal deliverypressure of said circulation pump to maintain said second named valveopen as long as the circulation pump produces said normal pressure; avalve in the aforesaid piping connecting the feed pump to the steamgenerating tubes, said third named valve being located beyond theconnection of said branch pipe with the piping in the direction of waterilow from the feed pump therethrough; means responsive to the normaldelivery pressure of said circulation pump to maintain said third namedvalve closed as long as the circulation pump produces said normalpressure; and means responsive to the difference between the circulationpump discharge and separator pressures for respectively closing andopening the second and third mentioned valves in the lines connectingthe feed pump to said separator and to said tubes upon outage of saidcirculation pump.

8. In a steam boiler having steam generating tubes connected todischarge into a separating drum to which a circulation pump isconnected for supplying said tubes through a pipe With water taken fromsaid drum, and a second pump connected by piping to supply feed Water tosaid drum; a self-closing valve in said piping; means responsive to theproduction of normal discharge pressure by the circulation pump formaintaining said valve open; a conduit connecting said piping at a pointahead of the valve therein in the direction of water ilow with theadmission ends of said tubes; a valve in said conduit arranged to openupon decrease of said circulation pump delivery pressure below normal;and a check valve in said pipe disposed to be opened by said normal pumpdischarge pressure.

ROBERT M. NALVEN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number

